The present invention relates to a retractable safety syringe, and more particularly, to a braking mechanism to resist a retraction force during normal operation of the retractable safety syringe until a piston head engages a needle holder and needle to then withdraw the needle holder and needle within the safety syringe body.
Retractable safety syringes are known in the art. For example, one type of retractable safety syringe is disclosed in U.S. Pat. No. 6,413,236 issued to Van Dyke, the entire contents of which are incorporated herein by reference. In the '236 patent, a retractable safety syringe has a piston which engages a needle holder and needle and retracts the same via a retraction force created by a variable vacuum compartment. In the retractable safety syringe disclosed in the '236 patent, the user must continuously apply a thumb pressure on the thumb platform such that the piston is not inadvertently traversed to a retracted position during operation of the safety syringe. For example, the piston may be inadvertently traversed to the retracted position while medication is being filled in a variable fluid chamber, residual air is being ejected from the variable fluid chamber and medication is being injected into the patient. As such, the user or medical professional is required to receive additional training to operate the safety syringe properly and safely. Unfortunately, the additional training may be costly. Also, since the operation of the safety syringe is not intuitive or fool proof, mistakes may be made during operation of the safety syringe.
Accordingly, there is a need in the art for an improved safety syringe.